A credit card, cash card or the like may comprise a noncontact-type integrated circuit (IC) card which, as is well known in the art, is capable of effecting the transfer of information between itself and an external information storage medium by means of a device such as a card reader/writer without electrically contacting (e.g., by means of electrodes, pins, etc.) such device.
A conventional noncontact-type IC card 10 (FIGS. 7 and 8) generally comprises a printed circuit board 11 on which is mounted an IC chip 12 for controlling the operation of the card (including storing data). Also provided on the printed circuit board 11 is an electromagnetic coil 13 for supplying electric power to the IC chip 12 from an external power source, and an electromagnetic coil 14 for effecting transmission and reception of data between the IC chip 12 and a noncontact-type card reader/writer device 15 of an external information storage medium (not shown). The IC chip 12 and the electromagnetic coils 13, 14, together with the printed circuit board 11, are embedded in a protective package (or card body) 16 comprised of a dielectric resin material or the like.
A conventional noncontact-type reader/writer device 15 (FIG. 8) is designed to receive a noncontact-type IC card and comprises a printed circuit board 17 which has two electromagnetic coils 18, 19 provided thereon for respectively supplying electric power from an external source (not shown) and for effecting the transmission/reception of data. When an IC card is properly inserted into the reader/writer device, these coils 18, 19 correspond to and lie substantially opposite to the respective electromagnetic coils 13, 14 of the IC card 10.
In operation, the card reader/writer device 15 and the IC card 10 are properly aligned with each other, as shown in FIG. 8. The coils of the IC card 10 have the same spiral configuration as the coils of the card reader/writer device 15 so that, when the IC card is inserted and held in the card reader/writer, the centers of the coils 13, 14 of the IC card are respectively located substantially opposite the centers of the coils 18, 19 of the card reader/ writer. AC current flows from the external source to the power supplying electromagnetic coil 18 of the card reader/writer device 15 and, thus, is induced in the electromagnetic coil 13 of the IC card 10. This induced AC current is converted into DC current by a full-wave rectification circuit or a diode bridge circuit (not shown) in the IC chip 12 to provide electric power for a power supply in the chip. When the IC chip 12 is thus powered, transfer of data may be carried out between the IC card 10 and the card reader/writer 15 since the data transmitting/ receiving electromagnetic coil 19 of the card reader/ writer and the electromagnetic coil 14 of the IC card are electromagnetically coupled with each other.
In general, the magnitude of an induced electromotive force which is generated in an electromagnetically coupled coil is proportional to the number of turns of the coil and the spiral length of the coil. Thus, in order to achieve highly efficient and reliable data and energy transfer between the IC card and the reader/writer, it is desirable to maximize the number of turns and/or the overall spiral length of the electromagnetic coils of both the IC card and the card reader/writer device.
However, since the electromagnetic coils of both conventional IC cards and card reader/writers are formed by etching copper foil which is provided on the surface of printed circuit boards (and has a thickness of approximately 18-35 microns), the widths of the coil windings and the intervals between adjacent windings are both restricted by the state of the art accuracy of etching. Consequently, in conventional printed circuit board IC cards and card reader/writer devices, it has only been possible to reduce the winding widths and the winding intervals to approximately 50-150 microns.
As a result, attempts to produce IC cards which are capable of highly reliable and efficient transfer of data and power have been hindered in that the etched electromagnetic coils must be physically large in size, thus increasing the overall size of the card. Indeed, to achieve the desired reliability and efficiency, typical etched coils are as large as about one inch in diameter. Moreover, since a large printed circuit board is required to mount large electromagnetic coils thereon, the conventional IC card is vulnerable to bending and breakage. In addition, since the IC chip is mounted on the printed circuit board, the thickness of the conventional IC card is also large (e.g., on the order of several millimeters).